The present invention relates to a magnetic sensor, a magnetic head, and a biomagnetic sensor.
Magnetoresistive elements are known as magnetic sensors for use in thin-film magnetic recording/reproducing heads. In general, a magnetoresistive element applies a current between a magnetization-fixed layer and a magnetization free layer and therefore obtains high output. However, the magnetoresistive element obtains a signal, caused by the motion of a domain wall due to current-induced spin torque or the like, unnecessary for magnetic sensors.
On the other hand, spin accumulation (SA) magnetic sensors in which a magnetization free layer and a magnetization-fixed layer are formed on the same horizontal surface (a channel layer for accumulating spins) are known (refer to, for example, Patent References 1 and 2). For example, in the case of using a spin accumulation magnetic sensor in a thin-film magnetic recording/reproducing head, no current needs to be applied to a magnetization free layer detecting the external magnetic field of a magnetic recording medium or the like. That is, in the spin accumulation magnetic sensor, magnetic condition can be detected in the form of an output voltage using a spin current only.